Recovery of tar acids or phenols from tars or tar oils



Patented July 2, 194i) RECOVERY F TAR ACIDS OB PHENOLS FROM TABS OB TAB OILS Vittorio Molinari, Milan, Italy, assignor to Bake lite, Corporation, New York, N. Y., a corporation of Delaware No Drawing.

Application August 19, 19 38,

s SerlalNo. assess. (o1. zoo-627i This "invention relates to the recovery of tar acids or phenols from tars or tar oils such as coal tar, shale tar, lignite tar, wood tar, or their oils, tar oil obtained from the low temperature distillation of coal, mineral oil which containstar acid or oil from petroleum cracking processes, etc. a K

It is known to extract phenols, i. e., tar acids,

from tar oils by the 'use of caustics but this is m relatively costly due, among other factors, to the necessity of using and having to recover a large amount of the relatively expensive caustic, some of which is lost in every cycle and must be replaced. Other methods oi-recovering phenols invalve the addition of organic salt solutions to the tar 011. Some of these methods afford only a partial extraction'of the phenols while othersproduce phenols which are quite impure, the phenols irequently'being contaminated with up to. 35 or 40 per cent neutral oil.

The method of extracting tar acids of thepresent invention seeks to overcome the objections to the prior art by using relatively inexpensive reagents and thereby obtaining -a substantially complete extraction of the acids 'or phenols in her of steps. Pyridine or other organic base compounds present in the tar oils can also be separated by this process from neutral oil and phenols.

According to the present invention tar oil which contains neutral oil (hydrocarbon derivatives of benzol and naphthalene) tar acids and pyridine base compounds, is treated with a material made up of a solvent for the neutral oil, a solvent for the tar acids, an ingredient to form a salt with the pyridine and other base compounds and preferably another ingredient or repellent to prevent the neutral oil and its solvent from dissolving in the tar acid or taracid solvent. The solvents are furthermore so chosen that they are immiscible in order-that the solutionsformed will divide into two layers which can readily be separated. In. addition the solvents are of a type so that they can later be separated from their solutes and re- 45 turned ior the separation of further amounts of tar acids. 7

By the conjoint addition of solvents for tar acids and for neutral oil to crude tar oils, the process of tar acid extraction is materially simplilied while at the same time the purity of the acid iraction separated is greatly improved, particularly ii the solvents are oi an immiscible character. If either solvent is added alone, thefraction substantially pure'condition in a minimum numh to such an extent with the other traction that a subsequent treatment with another solvent becomes necessary; this dual treatment can be sube stantially avoided by the present process and a tar acid fractioh of improved purity obtained as well. The further inclusion of a salt-forming ingredient incorporates another step of purification taking place simultaneously with the tar acid extraction while in addition the extraction isbene fited through the formation of a tar acid solvent. m Purification of the tar acid fractionv is still further improved with the addition of an agent acting as a repellant for the neutral oil; because of the actionof the. solvents in causing a. separation, the repellent is ailorded an opportunity to u make the separation more complete. A solvent for the neutral oilcomplying with the purposes of this invention is one which disl 1 solves substantially no phenols or at least dissolves less phenols than the neutral oil and which has a characteristic differing. from that of the neutraloil to permit their separation later in the process. Solvents found suitable are aliphatichydrocarbons such as mineral oil, petroleum kerosene, gasoline, etc., or their derivatives for instance halogens, tetrachlor ethane, ethylene dichloride, trichiorethylene, trichlorethane, etc., preferably so chosen as to have a boiling point different from the boiling point of the neutral oil in order that they may be separated by simple distillation if desired. The amount'of solvent used is such that it easily dissolves all or the neutral oil. g

,A solvent for the tar acids is one which is insoluble in the neutral oil or the neutral oil solvent,

and has a characteristic enabling it to be separated from the phenols later in the process whereby the phenols are obtained and the solvent may be returned to the PIOCBSS. A suitable sol vent is a concentrated solution of a salt of an organic base in water or other appropriate liquid. I

" since the concentrated solution dissolves tar acids while a weak solution does not. A 70 per cent or 1 higher concentration satisfactorily but any I concentration that extracts and holds the phenols can be used. Sufllcient amount of this solvent isi used to dissolve substantially all of the tar acids, control tests being run in .a laboratory prior to commercial use with any given tar oil to determine the amount, which is usually from about to 40 per cent by volume of the tar-oil treated. Another ingredient of the material'added to the tar oil is a free-acid which reacts with organic bases to form salts. This acid addition is for. the removal of organic bases present in the tar oil,

' and the salts thus formed become part of the strong organic acids such as acetic, formic, etc.

The phenols, even though they be dissolved in a solvent which does not of itself dissolve neutral oil, carry some ,of the neutral oil into the solution. The neutral ofl will contaminate the phenols if not separated from them. To accom plish this separation, the material which is used to treat the tar oils includesa repellant for the neutral oil. The repellant should be soluble in the phenol and repel the neutral oil so that when absorbed into the combination of phenol and organic base salt that is formed, it forces out the neutral oil. Suitable repellants are found to be organic or inorganic salts of alkaline or alkaline earth bases such as sodium benzene sulphonates, sodium naphthalene sulphonates, sodium sulphate or perchlorate, calcium chloride, etc. All of these are soluble in water so that they may be separated from the tar acids later in the process.

In carrying out the process, the material made up of the previouslymentioned ingredients, is added to the tar oil and .thoroughlymixed. The mixtureis then permitted to stand whereupon two layers are formed. The upper layer contains the neutral oil and the aliphatic hydrocarbon solvent while the bottom layer contains the phenols dissolved in the organic base salt solution andalso the repellant. The top layer is withdrawn from the separating vessel and subjected to a simple distillation whereby the aliphatic hydrocarbon solvent is separated from the neutral oil and may be returned to the cycle, I being used to treat fresh quantities of crude tar oil. To extract the last traces of tar acids from the mixture of neutral oil and neutral oil solvent, this mixture can be washed with fresh tar acid solvent which may later be used in the first step of the process.

- The bottom layer containing the'phenols *and organic base salts is diluted with water (usually less than 50% of the original volume) gwhereupon the phenols rise to the top of the diluted solution and the organic base salts form the bottom layer together with the small amount of repellant. The phenols may then be withdrawn as the final product of the process and may, if

desired, bewashed with a small amount of acid to remove traces of bases. This acid may thereafter be used as aningredient for preparing the tar acid solvent in the jfirst step of the process; The dilute water solution of organic base salts and repellant may easily be concentrated by evaporation and returned to the cycle as the ingredient for separating phenols from fresh charges of tar oils. The pyridine or other base .salts which are thus formed in every cycle may be treated with-strong alkali to liberate and thereby recover the bases from the salts.

1 The only chemical which need'be supplied to I the process is a suflicient quantity of free acid to react with the organic bases. As previously indicated, there is ..a wide choice'of acids, the least expensive of which is probably sulphuric acid. If the organic bases are-not objectionable in the neutral oil, the free acid may be omitted since the pyridine or otherv bases will be separated from the phenols in the first separation, that is, they will remain dissolved in the neutral oil' and neutral -oil solvent. By the use of the free acid, the organic bases are first dissolved with and then recovered from the tar acid solvent as previously indicated.

.If an extremely pure tar acid is desired, the tar acid-organic salt solution may be washed before the water dilution, with fresh aliphatic hydrocarbon. This washing removes all traces of neutral oil. The last traces of the aliphatic hydrocarbon may be removed bygentle heating, preferably under vacuum, before the water dilution. With such a washing, thephenols which are obtained as final products of the process are approximately 98-99 per cent pure.

From the previous description, the principle of the invention-will readily be understood but for complete disclosure the following illustrative examples are given. Example 1 One liter of middle coal tar oil having a distillation range between 160 and 260 C. with a content of per cent oftar acid and 4 per cent pyridine or other coal tar bases, is mixed with .75 liter of an aliphatic hydrocarbon distilling between 120 and 160 C. (containing as identified oils principally octane, nonane, or mixtures), 250

cc. of a concentrated solution of sulfates of pyridine bases, 3 per cent free sulphuric acid and 0.5 per cent sodium benzene sulfonate.

Upon standing approximately 600 cc. of tar acid extracting solution containing the phenols and the pyridine bases will be obtained as the bottom layer. The solution is washed three times with 250 cc. of the same quality of aliphatic hydrocarbons which will be used for the next extraction.

The washed solution is heated to about 45-50 C. under vacuum to eliminate traces of aliphatic is no loss in phenols.

The aliphatic hydrocarbon can be reclaimed from the neutral oil by distillation in vacuum and used again. Example 2 One liter of low temperature distillation coal tar oilwith-a distillation range between 175 and 250 Cgwith a content of percent of tar acid and 3 per cent of pyridine or other coal tar bases is mixed with 0.60 liter of aliphatic hydrocarbon the used for the next extraction and by this there distilling between and C. (containing as identified oils principally octane, nonane, or

decane or'mixtures) 300 cc. of a concentrated solution containing triethanolamine sulphate, 2 percent-of sulphuric acid (free) and 0.5 per cent of sodium sulphate. 1'

The treatment in Example 1 is followed and phenols with the same purity and in proportional 76 amount are obtained. The tar acid. extracting solution can be reclaimed by concentration and used again for another extraction. The aliphatic hydrocarbons can be reclaimed from the neutral oil by distillation in vacuum.

Eazample 3 One liter of lignite tar oil having a distillation chloride, 1.5 per cent hydrochloric acid (freer and 1 per cent calcium chloride.

The treatment in Example 1 is followed and phenols with the same purity and in proportional amount are obtained. The tar acid extracting solution can be reclaimed by concentration and used again for a new operation. The neutral oil can be separated from the kerosene by distillation in vacuum in a still with a rectification column; the neutral oil distills over and the kerosene remains as a residue in the still. It can be used again for a new operation.

The amounts, proportions, and kind of the various materials in the fluid extracting solution may be varied within wide limits depending upon the quality of the tar or tar oil as determined by a control laboratory.

If the tar oil contains more or less tar acid or neutral oil, or organic bases, the amount and characteristics of the solvents will be changed accordingly. The invention is not limited-to the quantity or quality of the salt of the organic base used, such as primary, secondary, etc., aliphatic or aromatic compounds, nor to the quality or quantity of the alkali or alkali earth salt used in the extracting solution, nor limited to the quality or quantity of the free acid present in the extracting fluid.

I claim:

1. In a method of separating tar acids from crude tar oils including organic bases, tar acids and neutral oils, the step which comprises treating a tar oil with a mixture including a free acid, asolvent for tar acids and a solvent for neutral oils, said solvents being substantially immiscible.

.2. In a method of separating tar acids from crude tar oils including tar acids and neutral oils, the step which comprises treating a taroil with a mixture including a solvent for tar acids, a solvent for neutral oils and a repellant to decrease the solubility of the neutral oil in the combination of tar acid and tar acid solvent, said solvents being substantially immiscible.-

3. In a method of separating tar acids from crude tar oils including organic bases, tar'acids and neutral oils, the step which comprises treating a tar oil with a mixture including a solvent for tar acids, a solvent for neutral oils and an ingredient to render the bases soluble in the tar ,acid solvent, said solvents being substantially immiscible in the presence of their solutes, and

separating the solvents with their respective solutes.

4. In a method of separating tar acids from crude tar oils including tar acids and neutral oils, the step which comprises treating a tar oil with a mixture including a solvent for tar acids and a' solvent for neutral oils, said solvents being separable in the presence of their solutes, separating the solvents with their respective solutes,

washing the neutral oil solvent containing new,

tral oil with fresh tar acid solvent, and using this tar acid solvent to treat fresh quantities of tar oil.

VI'I'IORIO MOLINARI; 

